System and method for power control

ABSTRACT

A method of communicating in a wireless system includes receiving resource scheduling information indicating a location of a resource for transmitting a packet, an indication of a target power level, and an indication of a first bandwidth, receiving an indication of a first transmission power level, determining a second transmission power level in accordance with the target power level, and at least one of the first bandwidth and the first transmission power level, and transmitting the packet at the location of the resource with the second transmission power level.

This application claims the benefit of U.S. Provisional Application No.62/059,030, filed on Oct. 2, 2014, entitled “System and Method for PowerControl,” which application is hereby incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to digital communications, andmore particularly to a system and method for power control.

BACKGROUND

As the number of smartphones/tablets with WiFi connection capabilitykeeps growing, the density of access points (APs) and stations (STAs) isgetting higher, especially in urban areas. The high density of APs andSTAs makes WiFi system less efficient since the original WiFi system wasdesigned assuming a low density of APs and STAs. For example, thecurrent enhanced distributed channel access (EDCA-based) media accesscontrol (MAC) scheme will not work efficiently in an environment with ahigh density of APs and STAs. As a result, a new Study Group (SG) calledHigh Efficiency Wireless Local Area Network (WLAN) (HEW) was formed inIEEE 802.11 to improve system performance in high density environments.As a result of the study of the HEW SG, a Task Group called TGax wasformed in May 2014.

SUMMARY OF THE DISCLOSURE

Example embodiments provide a system and method for power control.

In accordance with an example embodiment, a method of communicating in awireless system is provided. The method includes receiving, by astation, resource scheduling information indicating a location of aresource for transmitting a packet, an indication of a target powerlevel, and an indication of a first bandwidth, receiving, by thestation, an indication of a first transmission power level, determining,by the station, a second transmission power level in accordance with thetarget power level, and at least one of the first bandwidth and thefirst transmission power level, and transmitting, by the station, thepacket at the location of the resource with the second transmissionpower level.

In accordance with another example embodiment, a method of communicatingin a wireless system is provided. The method includes transmitting, byan access point, resource allocation information indicating a locationof a resource for transmitting a packet, an indication of a target powerlevel, and an indication of a first bandwidth, transmitting, by theaccess point, an indication of a first transmission power level, andreceiving, by the access point, the packet at the location of theresource.

In accordance with another example embodiment, a station adapted toperform power control is provided. The station includes a receiver, aprocessor operatively coupled to the receiver, and a transmitteroperatively coupled to the processor. The receiver receives resourcescheduling information indicating a location of a resource fortransmitting a packet, an indication of a target power level, and anindication of a first bandwidth, and receives an indication of a firsttransmission power level. The processor determines a second transmissionpower level in accordance with the target power level, and at least oneof the first bandwidth and the first transmission power level. Thetransmitter transmits the packet at the location of the resource withthe second transmission power level.

In accordance with another example embodiment, an access point isprovided. The access point includes a transmitter, and a receiveroperatively coupled to the transmitter. The transmitter transmitsresource allocation information indicating a location of a resource fortransmitting a packet, an indication of a target power level, and anindication of a first bandwidth, and transmits an indication of a firsttransmission power level. The receiver receives the packet at thelocation of the resource.

Practice of the foregoing embodiments enable transmission power controlin an asynchronous communications system with potentially dynamic systembandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example wireless communications system accordingto example embodiments described herein;

FIG. 2 illustrates a diagram of example channel access timing accordingto example embodiments described herein;

FIG. 3A illustrates a flow diagram of operations occurring in a firstexample embodiment of power control by an AP according to exampleembodiments described herein;

FIG. 3B illustrates a flow diagram of operations occurring in a firstexample embodiment of power control by a station according to exampleembodiments described herein;

FIG. 4 illustrates a message exchange diagram between an AP and astation as the two devices participate in power control in accordancewith the first example embodiment;

FIG. 5A illustrates a flow diagram of operations occurring in a secondexample embodiment of power control by an AP according to exampleembodiments described herein;

FIG. 5B illustrates a flow diagram of operations occurring in a secondexample embodiment of power control by a station according to exampleembodiments described herein;

FIG. 6A illustrates a flow diagram of operations occurring in a thirdexample embodiment of power control by an AP according to exampleembodiments described herein;

FIG. 6B illustrates a flow diagram of operations occurring in a thirdexample embodiment of power control by a station according to exampleembodiments described herein; and

FIG. 7 is a block diagram of a processing system that may be used forimplementing the devices and methods disclosed herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operating of the current example embodiments and the structurethereof are discussed in detail below. It should be appreciated,however, that the present disclosure provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificstructures of the embodiments and ways to operate the embodimentsdisclosed herein, and do not limit the scope of the disclosure.

One embodiment relates to power control. For example, a station receivesresource scheduling information indicating a location of a resource fortransmitting a packet, an indication of a target power level, and anindication of a first bandwidth, receives an indication of a firsttransmission power level, determines a second transmission power levelin accordance with the target power level, and at least one of the firstbandwidth and the first transmission power level, and transmits thepacket at the location of the resource with the second transmissionpower level.

The embodiments will be described with respect to example embodiments ina specific context, namely communications systems that are asynchronouswith potentially dynamic system bandwidth but uses power control toimprove communications performance. The embodiments may be applied tostandards compliant communications systems, such as those that arecompliant with IEEE 802.11, and the like, technical standards, andnon-standards compliant communications systems, that are asynchronouswith potentially dynamic system bandwidth but uses power control toimprove communications performance.

FIG. 1 illustrates an example wireless communications system 100.Wireless communications system 100 includes an access point (AP) 105that serves one or more stations, such as stations (STA) 110-116, byreceiving communications originating from the stations and thenforwarding the communications to their intended destinations orreceiving communications destined to the stations and then forwardingthe communications to their intended stations. In addition tocommunicating through AP 105, some stations may directly communicatewith one another. As an illustrative example, station 116 may transmitdirectly to station 118. While it is understood that communicationssystems may employ multiple APs capable of communicating with a numberof stations, only one AP, and a number of stations are illustrated forsimplicity.

Transmissions to and/or from a station occur on a shared wirelesschannel. WLANs make use of carrier sense multiple access with collisionavoidance (CSMA/CA), where a station desiring to transmit needs tocontend for access to the wireless channel before it can transmit. Astation may contend for access to the wireless channel using a networkallocation vector (NAV). The NAV may be set to a first value torepresent that the wireless channel is busy and to a second value torepresent that the wireless channel is idle. The NAV may be set bystation in accordance with physical carrier sensing and/or reception oftransmissions from other stations and/or APs. Therefore, contending foraccess to the wireless channel may require the station to expend asignificant amount of time, thereby decreasing wireless channelutilization and overall efficiency. Furthermore, contending for accessto the wireless channel may become difficult if not impossible as thenumber of stations contending for access increases.

FIG. 2 illustrates a diagram 200 of example channel access timing. Afirst trace 205 represents channel access for a first station (STA 1), asecond trace 207 represents channel access for a second station (STA 2),and a third trace 209 represents channel access for a third station (STA3). A short inter-frame space (SIFS) has a duration of 16 microseconds,a point coordination function (PCF) inter-frame space (PIFS) has aduration of 25 microseconds, while a distributed inter-frame space(DIFS) may last longer than either the SIFS or the PIFS. A backoffperiod may be a random duration. Therefore, active scanning may notprovide the best solution when there are large numbers of stationsattempting to perform AP/network discovery.

In cellular communications systems, e.g., 3GPP LTE compliantcommunications systems, orthogonal frequency division multiple access(OFDMA) has been shown to be able to provide robust performance in highdensity environments. OFDMA has the ability to support multiple userssimultaneously by carrying traffic from different users on differentportions of the communications system bandwidth. In general, OFDMA cansupport a large number of users more efficiently, especially when datatraffic from individual users is low. Specifically, OFDMA can avoidwasting frequency resources if traffic from one user cannot fill theentirety of the communications system bandwidth by utilizing the unusedbandwidth to carry transmissions from other user(s). The ability toutilize unused bandwidth may become crucial as the communications systembandwidth continues to become wider.

Similarly, uplink multi-user multiple input multiple output (UL MU-MIMO)techniques have also been used in cellular communications systems, e.g.,3GPP LTE, to enhance communications system performance. UL MU-MIMOallows multiple users to simultaneously transmit on the sametime-frequency resource(s) with the transmissions being separated inspace (i.e., on different spatial streams).

To support OFDMA and UL MU-MIMO, the power of the received signal frommultiple stations at the AP receiver should be at an appropriate level,as shown in the following examples. For UL MU-MIMO, the power differenceof the received signal from multiple stations on the same time-frequencyresource should be within a reasonable range. Otherwise, if thedifference is too large, the interference from the stronger receivedsignal will overwhelm the weaker one, making UL MU-MIMO not workable.For OFDMA, due to implementation inaccuracies, there exists interferenceleaked from one resource unit to another, especially for those adjacentto each other. Therefore it is also important to maintain the powerdifference of the received signal from multiple stations to be within areasonable range to avoid the weaker one being overwhelmed by thestronger one.

UL transmission power control can be utilized to make sure that thepower of the received signal from multiple STAs at the AP receiver is atappropriate level. UL power control is also helpful to control theinterference among the overlapping basic service set (OBSS).

In LTE, UL transmission power control includes both closed loop and openloop power control. In closed loop power control, the enhanced Node B(eNB) sends a power control command to instruct the UE to increase ordecrease its UL transmission power. In open loop power control, the UEmeasures path loss (PL) between the eNB and itself based on the downlink(DL) reference signal (RS) measurement, and adjusts its UL transmissionpower according to the measured PL and other factors such as the size ofthe allocated UL resource and modulation coding scheme (MCS), etc.

However, in Wi-Fi system such as 11ax, the aforementioned UL powercontrol schemes may not work. Wi-Fi system is asynchronous, there is noa periodic UL control channel to enable the AP to perform UL receivedsignal measurement and generate closed loop power control commandaccordingly. In LTE, where the system bandwidth and the DL RS power areusually fixed, PL measurement is straightforward, done by comparing thetransmitted and received signal power of the DL RS. In a Wi-Fi system,the system bandwidth could be dynamic, e.g., varying from 20 MHz to 80MHz. And since a station may not be required to monitor the whole systembandwidth, it is not straightforward to measure the PL.

According to an example embodiment, a frame transmitted by an AP to astation includes a resource allocation and an indication of downlinktransmissions. The resource allocation includes information indicatingresources (e.g., frequency resource allocations) for an uplinktransmission allocated to the station as well as a target uplink receivepower. The indication of the downlink transmissions may include anindication of a downlink transmission power level for a transmissionmade by the AP, as well as an indication of a total downlink bandwidth.

FIG. 3A illustrates a flow diagram of operations 300 occurring in afirst example embodiment of power control by an AP. Operations 300 maybe indicative of operations occurring in an AP as the AP participates inpower control in accordance with the first example embodiment.

Operations 300 begin with the AP transmitting a frame, such as a triggerframe, including a resource allocation and an indication of downlinktransmissions (block 305). The resource allocation includes uplinkscheduling information, such as an indication of resources (e.g., one ormore frequency resource locations) for an uplink transmission allocatedto the station. The uplink scheduling information also includes anindication of a target uplink received power, P_(UL) _(_) _(RX) _(_)_(TARGET), for the station. The indication of downlink transmissions mayinclude an indication of a downlink transmission power level of thedownlink transmission including the frame, P_(DL) _(_) _(TX) _(_)_(TOTAL), as well as an indication of total downlink bandwidth of thedownlink transmission including the frame, BW_(DL) _(_) _(TOTAL). It isnoted that the downlink transmission may include more bandwidth than thebandwidth occupied by the frame. As an example, the frame may betransmitted in 20 MHz of bandwidth while the total downlink bandwidth is80 MHz. The remaining 60 MHz of bandwidth may be used for carrying otherdownlink frames. The AP receives a frame as indicated in the resourceallocation of the trigger frame (block 310).

FIG. 3B illustrates a flow diagram of operations 350 occurring in afirst example embodiment of power control by a station. Operations 350may be indicative of operations occurring in a station as the stationparticipates in power control in accordance with the first exampleembodiment.

Operations 350 begin with the station receiving a frame, such as atrigger frame, including a resource allocation and an indication ofdownlink transmissions (block 355). The resource allocation includesuplink scheduling information, such as an indication of resources (e.g.,one or more frequency resource locations) for an uplink transmissionallocated to the station. The uplink scheduling information alsoincludes an indication of a target uplink receive power, P_(UL) _(_)_(RX) _(_) _(TARGET), for the station. The indication of downlinktransmissions may include an indication of a downlink transmission powerlevel of the downlink transmission including the frame, P_(DL) _(_)_(TX) _(_) _(TOTAL), as well as an indication of total downlinkbandwidth of the downlink transmission including the frame, BW_(DL) _(_)_(TOTAL). It is noted that the downlink transmission may include morebandwidth than the bandwidth occupied by the frame. As an example, theframe may be transmitted in 20 MHz of bandwidth while the total downlinkbandwidth is 80 MHz. The remaining 60 MHz of bandwidth may be used forcarrying other downlink frames.

The station measures a downlink receive power of the frame, P_(DL) _(_)_(RX) (block 360). The downlink received power is measured only in thebandwidth occupied by the frame. The station derives a path loss betweenthe AP and the station in accordance with the downlink receive powerP_(DL) _(_) _(RX) (block 365). The path loss may be a difference betweenthe downlink transmission power and the downlink receive power. As anillustrative example, the path loss may be expressed aspath loss=P _(DL) _(_) _(TX) _(_) _(TOTAL)+10*log₁₀(BW_(DL)/BW_(DL) _(_)_(TOTAL))−P _(DL) _(_) _(RX),where BW_(DL) is the bandwidth of the frame, and10*log₁₀(BW_(DL)/BW_(DL) _(_) _(TOTAL)) is a scaling factor used whenthe power density in the downlink transmission is constant over theentire downlink bandwidth.

The station determines the uplink transmission power, P_(UL) _(_) _(TX),in accordance with the path loss and a maximum uplink transmission powerof the station, P_(UL) _(_) _(TX) _(_) _(MAX) (block 370). As anillustrative example, the uplink transmission power may be expressed asP _(UL) _(_) _(TX)=min(P _(UL) _(_) _(TX) _(_) _(MAX) ,P _(UL) _(_)_(RX) _(_) _(TARGET)+path loss),where min( ) is a minimum function that returns the minimum value of itsinput elements. The station transmits in the uplink in accordance withthe uplink scheduling information at an uplink transmit power equal toP_(UL) _(_) _(TX) (block 375). The transmission in the uplink may occurin a short interframe space (SIFS) after the end of the downlink frame.

FIG. 4 illustrates a message exchange diagram between an AP 405 and astation 410 as the two devices participate in power control inaccordance with the first example embodiment. AP 405 determines uplinkresource allocations for stations, as well as corresponding targetuplink receive powers (block 415). AP 405 transmits a frame in thedownlink, the frame carrying uplink scheduling information, as well asan indication of downlink transmissions (event 420). Station 410receives the frame and measures the downlink receive power of the frame,derives the path loss, and determines the uplink transmission power(block 425). Station 410 transmits in the uplink in accordance with theuplink scheduling information at an uplink transmit power (event 430).

As an illustrative example, consider a situation where a stationreceives a frame from an AP. For discussion purposes, assume that thestation measures the downlink receive power of the frame P_(DL) _(_)_(RX) to be −60 dBm, the frame is carried in 20 MHz of bandwidth andincludes uplink scheduling information, and the maximum uplinktransmission power of the station is 15 dBm. The frame also includes anindication that the total downlink bandwidth is 80 MHz, an indicationthat the downlink transmission power is 23 dBm, and the target uplinkreceive power is −67 dBm. The station may determine the path loss to bepath loss=P _(DL) _(_) _(TX) _(_) _(TOTAL)+10*log₁₀(BW_(DL)/BW_(DL) _(_)_(TOTAL))−P _(DL) _(_) _(RX),path loss=23 dBm+10*log₁₀(20 MHz/80 MHz)−(−60 dBm),path loss=77 dB.The station may then derive the uplink transmission power to beP _(UL) _(_) _(TX)=min(P _(UL) _(_) _(TX) _(_) _(MAX) ,P _(UL) _(_)_(RX) _(_) _(TARGET)+path loss),P _(UL) _(_) _(TX)=min(15 dBm,−67 dBm+77 dB),P _(UL) _(_) _(TX)=10 dBm.Therefore, in SIFS after the end of the frame, the station may start atransmission in the uplink with an uplink transmit power of 10 dBm onone or more resources indicated in the uplink scheduling information.

According to an example embodiment, in a situation where the totaldownlink transmission power is not evenly distributed across the totaldownlink bandwidth, the frame includes the downlink transmission powerfor only the bandwidth used to transmit the frame and not the downlinktransmission power for the entire bandwidth.

FIG. 5A illustrates a flow diagram of operations 500 occurring in asecond example embodiment of power control by an AP. Operations 500 maybe indicative of operations occurring in an AP as the AP participates inpower control in accordance with the second example embodiment.

Operations 500 begin with the AP transmitting a frame, such as a triggerframe, including a resource allocation and an indication of downlinktransmissions (block 505). The resource allocation includes uplinkscheduling information, such as an indication of resources (e.g., one ormore frequency resource locations) for an uplink transmission allocatedto the station. The uplink scheduling information also includes anindication of a target uplink received power, P_(UL) _(_) _(RX) _(_)_(TARGET), for the station. The indication of downlink transmissions mayinclude an indication of a downlink transmission power level of theframe, P_(DL) _(_) _(TX). It is noted that the downlink transmission mayinclude more bandwidth than the bandwidth occupied by the frame. As anexample, the frame may be transmitted in 20 MHz of bandwidth while thetotal downlink bandwidth is 80 MHz. The remaining 60 MHz of bandwidthmay be used for carrying other downlink frames. Unlike in the firstexample embodiment, the power density in the downlink transmission isnot constant. Hence, the AP indicates the transmit power level of theframe. The AP receives a frame as indicated in the resource allocationof the trigger frame (block 510).

FIG. 5B illustrates a flow diagram of operations 550 occurring in asecond example embodiment of power control by a station. Operations 550may be indicative of operations occurring in a station as the stationparticipates in power control in accordance with the second exampleembodiment.

Operations 550 begin with the station receiving a frame, such as atrigger frame, including a resource allocation and an indication ofdownlink transmissions (block 555). The resource allocation includesuplink scheduling information, such as an indication of resources (e.g.,one or more frequency resource locations) for an uplink transmissionallocated to the station. The uplink scheduling information alsoincludes an indication of a target uplink receive power, P_(UL) _(_)_(RX) _(_) _(TARGET), for the station. The frame also includes anindication of downlink transmissions. The indication of downlinktransmissions may include an indication of a downlink transmission powerlevel of the frame, P_(DL) _(_) _(TX).

The station measures a downlink receive power of the frame, P_(DL) _(_)_(RX) (block 560). The downlink received power is measured only in thebandwidth occupied by the frame. The station derives a path loss betweenthe AP and the station in accordance with the downlink receive powerP_(DL) _(_) _(RX) (block 565). The path loss may be a difference betweenthe downlink transmission power and the downlink receive power. As anillustrative example, the path loss may be expressed aspath loss=P _(DL) _(_) _(TX) −P _(DL) _(_) _(RX).Since the power density of the downlink transmission is not constant,the power level for the frame may be different from the power levels ofother portions of the downlink transmission.

The station determines the uplink transmission power, P_(UL) _(_) _(TX),in accordance with the path loss and a maximum uplink transmission powerof the station, P_(UL) _(_) _(TX) _(_) _(MAX) (block 570). As anillustrative example, the uplink transmission power may be expressed asP _(UL) _(_) _(TX)=min(P _(UL) _(_) _(TX) _(_) _(MAX) ,P _(UL) _(_)_(RX) _(_) _(TARGET)+path loss),where min( ) is a minimum function that returns the minimum value of itsinput elements. The station transmits in the uplink in accordance withthe uplink scheduling information at an uplink transmit power equal toP_(UL) _(_) _(TX) (block 575). The transmission in the uplink may occurin a SIFS after the end of the downlink frame.

According to an example embodiment, a frame transmitted by an AP to astation includes a resource allocation but does not include anindication of the downlink transmission power or the downlinktransmission power for the bandwidth used to transmit the frame, whichis transmitted in a different frame. In situations where the downlinktransmission power or the downlink transmission power for the bandwidthused to transmit the frame remains relatively constant for an extendedamount of time, the communications overhead may be reduced byeliminating the indication of the total downlink transmission power orthe downlink transmission power for the bandwidth used to transmit theframe. The indication of the total downlink transmission power or thedownlink transmission power for the bandwidth used to transmit the framemay be carried in a system information frame, such as a beacon frame.The resource allocation (including information indicating resources(e.g., frequency resource allocations) for an uplink transmissionallocated to the station as well as a target uplink receive power) istransmitted in another frame, such as a trigger frame.

FIG. 6A illustrates a flow diagram of operations 600 occurring in athird example embodiment of power control by an AP. Operations 600 maybe indicative of operations occurring in an AP as the AP participates inpower control in accordance with the third example embodiment.

Operations 600 begin with the AP transmitting a first frame, such as asystem information frame, including an indication of downlinktransmission power level (block 605). The downlink transmission powerlevel may be for the entire downlink transmission (such as when thepower density of the entire downlink transmission is constant) or thebandwidth used to transmit the first frame (such as when the powerdensity of the downlink transmission is not constant over thebandwidth). The AP transmits a second frame, such as a trigger frame,including a resource allocation and an indication of downlinktransmissions (block 610). The resource allocation includes uplinkscheduling information, such as an indication of resources (e.g., one ormore frequency resource locations) for an uplink transmission allocatedto the station. The uplink scheduling information also includes anindication of a target uplink received power, P_(UL) _(_) _(RX) _(_)_(TARGET), for the station. The indication of downlink transmissions mayinclude an indication of a total downlink bandwidth, BW_(DL) _(_)_(TOTAL). The AP receives a frame as indicated in the resourceallocation of the trigger frame (block 615).

FIG. 6B illustrates a flow diagram of operations 650 occurring in athird example embodiment of power control by a station. Operations 650may be indicative of operations occurring in a station as the stationparticipates in power control in accordance with the third exampleembodiment.

Operations 650 begin with the station receiving a first frame, such as asystem information frame, including an indication of downlinktransmission power level (block 655). Since the downlink transmissionpower level remains relatively constant, it may not be necessary toinclude it in each downlink transmission, thereby reducingcommunications overhead. The station receives a second frame, such as atrigger frame, including a resource allocation and an indication ofdownlink transmissions (block 660). The resource allocation includesuplink scheduling information, such as an indication of resources (e.g.,one or more frequency resource locations) for an uplink transmissionallocated to the station. The uplink scheduling information alsoincludes an indication of a target uplink receive power, P_(UL) _(_)_(RX) _(_) _(TARGET), for the station. The frame also includes anindication of downlink transmissions. The indication of downlinktransmissions may include an indication of total downlink bandwidth ofthe downlink transmission including the frame, BW_(DL) _(_) _(TOTAL).

The station measures a downlink receive power of the frame, P_(DL) _(_)_(RX) (block 665). The downlink received power is measured only in thebandwidth occupied by the frame. The station derives a path loss betweenthe AP and the station in accordance with the downlink receive powerP_(DL) _(_) _(RX) (block 670). The path loss may be a difference betweenthe downlink transmission power and the downlink receive power. As anillustrative example, the path loss may be expressed aspath loss=P _(DL) _(_) _(TX) _(_) _(TOTAL)+10*log₁₀(BW_(DL)/BW_(DL) _(_)_(TOTAL))−P _(DL) _(_) _(RX),where BW_(DL) is the bandwidth of the frame, and10*log₁₀(BW_(DL)/BW_(DL) _(_) _(TOTAL)) is a scaling factor used whenthe power density in the downlink transmission is constant over theentire downlink bandwidth.

The station determines the uplink transmission power, P_(UL) _(_) _(TX),in accordance with the path loss and a maximum uplink transmission powerof the station, P_(UL) _(_) _(TX) _(_) _(MAX) (block 675). As anillustrative example, the uplink transmission power may be expressed asP _(UL) _(_) _(TX)=min(P _(UL) _(_) _(TX) _(_) _(MAX) ,P _(UL) _(_)_(RX) _(_) _(TARGET)+path loss),where min( ) is a minimum function that returns the minimum value of itsinput elements. The station transmits in the uplink in accordance withthe uplink scheduling information at an uplink transmit power equal toP_(UL) _(_) _(TX) (block 680). The transmission in the uplink may occurin a SIFS after the end of the downlink frame.

According to an example embodiment, it is possible to combine two ormore of the example power control techniques presented herein. As anillustrative example, in a situation wherein the total downlinkbandwidth of the downlink transmission including the frame is notconstant but remains relatively unchanged over time, it is possible toinclude an indication of the total downlink bandwidth of the downlinktransmission including the frame in a system information frame (acombination of the second example power control technique and the thirdexample power control technique).

FIG. 7 is a block diagram of a processing system 700 that may be usedfor implementing the devices and methods disclosed herein. In someembodiments, the processing system 700 comprises a UE. Specific devicesmay utilize all of the components shown, or only a subset of thecomponents, and levels of integration may vary from device to device.Furthermore, a device may contain multiple instances of a component,such as multiple processing units, processors, memories, transmitters,receivers, etc. The processing system may comprise a processing unit 705equipped with one or more input/output devices, such as a humaninterface 715 (including speaker, microphone, mouse, touchscreen,keypad, keyboard, printer, and the like), display 710, and so on. Theprocessing unit may include a central processing unit (CPU) 720, memory725, a mass storage device 730, a video adapter 735, and an I/Ointerface 740 connected to a bus 745.

The bus 745 may be one or more of any type of several bus architecturesincluding a memory bus or memory controller, a peripheral bus, videobus, or the like. The CPU 720 may comprise any type of electronic dataprocessor. The memory 725 may comprise any type of system memory such asstatic random access memory (SRAM), dynamic random access memory (DRAM),synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof,or the like. In an embodiment, the memory 725 may include ROM for use atboot-up, and DRAM for program and data storage for use while executingprograms.

The mass storage device 730 may comprise any type of storage deviceconfigured to store data, programs, and other information and to makethe data, programs, and other information accessible via the bus 745.The mass storage device 730 may comprise, for example, one or more of asolid state drive, hard disk drive, a magnetic disk drive, an opticaldisk drive, or the like.

The video adapter 735 and the I/O interface 740 provide interfaces tocouple external input and output devices to the processing unit 700. Asillustrated, examples of input and output devices include the display710 coupled to the video adapter 735 and the mouse/keyboard/printer 715coupled to the I/O interface 740. Other devices may be coupled to theprocessing unit 700, and additional or fewer interface devices may beutilized. For example, a serial interface such as Universal Serial Bus(USB) (not shown) may be used to provide an interface for a printer.

The processing unit 800 also includes one or more network interfaces750, which may comprise wired links, such as an Ethernet cable or thelike, and/or wireless links to access nodes or different networks 755.The network interface 750 allows the processing unit 700 to communicatewith remote units via the networks 755. For example, the networkinterface 750 may provide wireless communication via one or moretransmitters/transmit antennas and one or more receivers/receiveantennas. In an embodiment, the processing unit 700 is coupled to alocal-area network or a wide-area network 755 for data processing andcommunications with remote devices, such as other processing units, theInternet, remote storage facilities, or the like.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims.

What is claimed is:
 1. A method of communicating in a wireless system, the method comprising: receiving, by a station, resource scheduling information indicating a location of a resource for transmitting a packet, an indication of a target power level, and an indication of a first bandwidth, wherein the indication of the target power level is used to indicate a target uplink receive power of the packet; receiving, by the station, an indication of a first transmission power level, wherein the indication of the first transmission power level is used to indicate a transmit power of a downlink transmission; measuring, by the station, a receive power level in accordance with the downlink transmission; determining a path loss, in accordance with the receive power level and at least one of the first bandwidth and the first transmission power level; determining, by the station, a second transmission power level, in accordance with the target power level and the path loss; and transmitting, by the station, the packet at the location of the resource and at the second transmission power level.
 2. The method of claim 1, the resource scheduling information, the indication of the target power level, and the indication of the first bandwidth are received in a first frame and the indication of the first transmission power level is received in a second frame.
 3. The method of claim 2, wherein the first frame is a trigger frame and the second frame is a beacon frame.
 4. The method of claim 2, wherein the first frame and the second frame are received at different times.
 5. The method of claim 1, wherein the resource scheduling information, the indication of the target power level, the indication of the first bandwidth and the indication of the first transmission power level are received in one frame.
 6. The method of claim 1, wherein determining the path loss comprises evaluating PL=P _(DL) _(_) _(TX) _(_) _(TOTAL)+10*log₁₀(BW_(DL)/BW_(DL) _(_) _(TOTAL))−P _(DL) _(_) _(RX), where PL is the path loss, P_(DL) _(_) _(TX) _(_) _(TOTAL) is the first transmission power level, P_(DL) _(_) _(RX) is the receive power level, BW_(DL) is a second bandwidth used to measure the receive power level, and BW_(DL) _(_) _(TOTAL) is the first bandwidth.
 7. The method of claim 6, wherein the resource scheduling information, the indication of the target power level, and the indication of the first bandwidth are received on the second bandwidth.
 8. The method of claim 6, wherein determining the second transmission power level in accordance with the path loss comprises evaluating P _(UL) _(_) _(TX)=min(P _(UL) _(_) _(TX) _(_) _(MAX) ,P _(UL) _(_) _(RX) _(_) _(TARGET)+PL), where P_(UL) _(_) _(TX) is the second transmission power level, P_(UL) _(_) _(TX) _(_) _(MAX) is a maximum value of the second transmission power level, P_(UL) _(_) _(RX) _(_) _(Target) is the target power level, PL is the path loss, and min( ) is a minimum function which returns a minimum value of its input elements.
 9. The method of claim 1, wherein determining the path loss comprises evaluating PL=P _(DL) _(_) _(TX) −P _(DL) _(_) _(RX), where PL is the path loss, and P_(DL) _(_) _(TX) is the first transmission power level, P_(DL) _(_) _(RX) is the receive power level.
 10. A station adapted to perform power control, the station comprising: a receiver configured to receive resource scheduling information indicating a location of a resource for transmitting a packet, an indication of a target power level, and an indication of a first bandwidth, and to receive an indication of a first transmission power level, wherein the indication of the target power level is used to indicate a target uplink receive power of the packet, and the indication of the first transmission power level is used to indicate a transmit power of a downlink transmission; a processor operatively coupled to the receiver, the processor configured to measure a receive power level, to determine a path loss in accordance with the receive power level and at least one of the first bandwidth and the first transmission power level, to determine a second transmission power level in accordance with the target power level and the path loss, wherein the receive power level is measured in accordance with the downlink transmission; and a transmitter operatively coupled to the processor, the transmitter configured to transmit the packet at the location of the resource and at the second transmission power level.
 11. The station of claim 10, wherein the processor is configured to evaluate PL=P _(DL) _(_) _(TX) _(_) _(TOTAL)+10*log₁₀(BW_(DL)/BW_(DL) _(_) _(TOTAL))−P _(DL) _(_) _(RX), where PL is the path loss, P_(DL) _(_) _(TX) _(_) _(TOTAL) is the first transmission power level, P_(DL) _(_) _(RX) is the receive power level, BW_(DL) is a second bandwidth used to measure the receive power level, and BW_(DL) _(_) _(TOTAL) is the first bandwidth.
 12. The station of claim 11, wherein the processor is configured to evaluate P _(UL) _(_) _(TX)=min(P _(UL) _(_) _(TX) _(_) _(MAX) ,P _(UL) _(_) _(RX) _(_) _(TARGET)+PL), where P_(UL) _(_) _(TX) is the second transmission power level, P_(UL) _(_) _(TX) _(_) _(MAX) is a maximum value of the second transmission power level, P_(UL) _(_) _(RX) _(_) _(Target) is the target power level, PL is the path loss, and min( ) is a minimum function which returns a minimum value of its input elements.
 13. The station of claim 10, wherein the processor is configured to evaluate PL=P _(DL) _(_) _(TX) −P _(DL) _(_) _(RX), where PL is the path loss, and P_(DL) _(_) _(TX) is the first transmission power level, P_(DL) _(_) _(RX) is the receive power level.
 14. The station of claim 10, wherein the resource scheduling information, the indication of the target power level, and the indication of the first bandwidth are received in a trigger frame and the indication of the first transmission power level is received in a beacon frame.
 15. The station of claim 10, wherein the resource scheduling information, the indication of the target power level, the indication of the first bandwidth and the indication of the first transmission power level are received in one frame. 